C# DLL not updated on rebuild after system time manipulation

[SmallKi]

Tested versions

• Reproduciable in v4.5.1.stable.mono.official [f62fdbd]

System information

Windows10 - Godot-v4.5.1.stable.mono.official [f62fdbd]

Issue description

I've encountered a potential bug in the Godot C# version where modifying the system time can prevent subsequent C# code changes from being reflected in the built DLL.

Steps to reproduce

1. Have a Godot C# project with some existing C# scripts.
2. Change the system time on your local machine forward (e.g., from 2025-11-18 to 2025-11-20).
3. Make a trivial change to a C# script (e.g., add a comment, modify a variable) and build the project within Godot. Observe that the build succeeds.
4. Change the system time back to its original/correct time.
5. Make another distinct change to the same or a different C# script, for example, print "hello world" in '_Ready'. Build the project again.
6. Start the game in editor, no print showing in output panel.
7. Move to .godot\mono\temp\bin\Debug , the dll's last update time is 2025-11-20, not 2025-11-18

Minimal reproduction project (MRP)

show in steps

[SmallKi]

Currently, this issue can be temporarily worked around by manually deleting the .dll file before rebuilding. However, the core problem is that the build tool incorrectly assumes the existing .dll is up-to-date and skips overwriting it. This is particularly misleading because the build process reports success, giving the false impression that the latest code has been applied.
To address this, could we have an option to either:
Force overwrite the .dll on every build, ensuring the latest code is always used?
Or, show warning if there has a newer build result after rebuilding, and provide a manual "Clean" button within the editor to clear previous build artifacts?

[AR-DEV-1]

May be an issue with the buildsystem, seems weird. By default, the latest dll should be compiled,

[AR-DEV-1]

Can you please confirm this in a dev build of 4.6?

[SmallKi]

Can you please confirm this in a dev build of 4.6?

Yes, confirmed on 4.6 dev4

[SmallKi]

By the way, my dotnet version is 9.0.306

[AThousandShips]

I'm not sure this is at all a Godot issue, this is probably just visual studio and the configuration using the file timestamps to control rebuilding, not sure if there's anything here we can do about it unless it's the editor side code that causes this

And most of the time this won't matter at all unless users intentionally trigger it

[AR-DEV-1]

I agree, not sure myself. May be an issue in C#. I searched through the files but couldn't find anything,

[skorpnok]

👍 for adding a menu option for a clean rebuild.
But other than that this just seems like the intended behaviour. Beyond the timestamp the build system has no way of knowing which is newer (without say storing a hash for each source file, which would increase build times for no clear benefit).

[AThousandShips]

Let's keep this open until we can establish if there's anything in the editor itself that can be changed, but I don't expect there is, for adding a force rebuild menu option please open a proposal or discussion instead

[raulsntos]

This would be MSBuild deciding whether the assembly is up to date, so not really something to do with Godot, as others have mentioned.

Regarding a clean/rebuild option, this already exists, see the MSBuild panel: